Turbomachine for compressing a fluid

ABSTRACT

A turbomachine for use as a compressor has a tubular housing centered on an axis, a rotor at least generally centered on the axis in the housing, and bearings supporting the rotor in the housing for rotation about the axis. The rotor is formed by a small-diameter shaft extending along and centered on the axis, formed with at least one mounting collar, and carried by the bearings, and by a plurality of annular disks fitted axially together and formed with radially outwardly extending vanes. At least one of the disks is fitted with and secured to the mounting collar.

FIELD OF THE INVENTION

The present invention relates to a turbomachine. More particularly this invention concerns such a machine used for compressing a fluid.

BACKGROUND OF THE INVENTION

A typical turbomachine has a stationary housing with a passage-forming chamber extending along an axis and holding a rotor having a body supported by bearings for rotation about the axis. Axially extending vanes or blades also projecting radially outward from an outer surface of the rotor body and compress a fluid while moving it axially through the housing.

Turbomachines used in industrial applications, e.g., chemical or petrochemical plants frequently operate under precisely controllable conditions within a predefined throughput and rotational-speed range. The rotors are optimized for this operating point and are formed by a solid shaft to which the rotor blades are attached. Producing and balancing this type of rotor arrangement is expensive. To this end, a fluid-lubricated bearing system is provided, such as, for example, oil-lubricated system, thereby necessitating an effective sealing system to prevent lubricants from contaminating the fluid flowing through the turbomachine.

Disks formed with the turbomachine blades, known as blisks, are well known in the aircraft production industry. Turbomachine blades that are integrated into a disk allow a considerable amounts of material to be saved that is then not required for assembling and adjusting the individual blades. It is possible, in particular, to form voids at the center of the disks. The consequence of this, however, is that stacking multiple blisks means that individual production and assembly tolerances are cumulative, thereby requiring a more robust bearing arrangement and resulting in restrictions in terms of the maximum allowable rotational speed.

OBJECTS OF THE INVENTION

It is therefore an object of the present invention to provide an improved turbomachine for compressing a fluid.

Another object is the provision of such an improved turbomachine for compressing a fluid that overcomes the above-given disadvantages, in particular that can properly function using a small bearing arrangement and can be operated a high speeds.

SUMMARY OF THE INVENTION

A turbomachine for use as a compressor has a tubular housing centered on an axis, a rotor at least generally centered on the axis in the housing, and bearings supporting the rotor in the housing for rotation about the axis. The rotor is formed by a small-diameter shaft extending along and centered on the axis, formed with at least one mounting collar, and carried by the bearings, and by a plurality of annular disks fitted axially together and formed with radially outwardly extending vanes. At least one of the disks is fitted with and secured to the mounting collar.

In practice there are two such collars and only the end disks engage the collars. The intermediate disks have no radial contact with the shaft of the rotor. The selected diameter of the shaft is as small as possible so as to reduce the overall mass of the rotor. At the same time, however, the diameter is dimensioned so as to ensure a reliable transmission of force and dimensional accuracy of the rotor under all anticipated operating states.

The mounting collar is integrally formed with the shaft and projects radially from it. The package consisting of rotor disks is attached to the shaft by the collar. Disks of this type with integrated rotor blades are also known as a bladed integrated disk (blisk) and are produced as a single piece, generally by machining. The disks are annular and have a center hole concentric with an outer circumferential surface, one section of the thin shaft running at the center through the hole with spacing when installed. A clearance is provided between the shaft and an inner periphery of the blisks.

According to the invention, the rotor is supported by bearings in the housing. The interaction of a thin central shaft, a lightweight structural design of the rotor, the use of precisely balanced blisks and low-friction bearings provides extremely smooth running characteristics for the rotor, and enables the turbomachine to be operated at very high speeds in industrial applications.

At least parts of the bearing arrangement are preferably provided in the form of magnetic bearings. A magnetic bearing arrangement is possible due to the fact that the use of blisks allows the mass of the rotor to be reduced to the point is where the use of magnetic bearings is economically feasible. The design using only magnetic bearings has the additional advantage of completely eliminating the need for lubricants.

In other preferred embodiments, at least some of the bearings are implemented in the form of rolling contact bearings, hydrodynamic plain bearings, or hydrostatic plain bearings.

Two collars are preferably integrally molded onto the shaft, a narrow region being disposed between these surfaces. One of each terminal disks of the package contacts the two collars and/or is attached to this. The two terminal disks here can be attached to the two collars, and the package of disks can be braced between these.

In one arrangement comprising two collars, the rotor is preferably supported axially and radially on bearings that are disposed outside the projections with the collars. The bearings can be provided here in the form of separate bearings or as combined thrust/radial bearings.

The turbomachine is preferably implemented at least in part as an axial design. The gaseous or vaporous fluid in this case flows at least in part in a direction parallel to the rotational axis of the rotor. It is additionally possible to also provide elements of radially operating turbomachines.

In a preferred embodiment, the disks of the rotor include mounting flanges forming radially stepped shoulders. The stepped shoulders of adjacent disks engage complementarily with each other. Stacked disks are effectively precluded by this attachment from sliding laterally (radially). This produces reliable stiffness even in a package in which only the end disks are braced against each other. In addition, respective immediately successive disks can also be attached to each other in pairs, for example, by means of bolts.

The disks of the rotor advantageously include regions at the center without turbomachine blades of different diameters.

The regions without turbomachine blades of the rotor's disk radially delimit a common circumferential area that is rotationally symmetrical about the center of rotation and is tapered. The uniform taper in the cross-section means that no unwanted turbulence occurs at discontinuous diameter transitions in the turbomachine.

BRIEF DESCRIPTION OF THE DRAWING

The above and other objects, features, and advantages will become more readily apparent from the following description, reference being made to the accompanying drawing in which:

FIG. 1 is a longitudinal section through a turbomachine according to the invention; and

FIG. 2 is a large-scale sectional view of the bearing region of the invention.

SPECIFIC DESCRIPTION OF THE INVENTION

As seen in FIG. 1 a turbomachine according to the invention for compressing a gas or vapor has a housing 1 here shown schematically by a dot-dash line and a rotor 2 rotationally supported on bearings 3 and 4 for rotation about an axis 10 in the housing 1. According to the invention, the rotor 2 has a small-diameter shaft 5 as well as a set of disks 6 a-6 e with integrated rotor blades of which one is shown schematically at 14. Two radially outwardly projecting collars 7 a and 7 b are integrally formed on the shaft 5 and are the only locations where the rotor 2 is attached to the shaft 5. Only the two end disks 6 a and 6 e are fixed to the respective collars 7 a and 7 b. The shaft 5 is supported in the housing 1 by axial magnetic bearings 3 and radial magnetic bearings 4.

The disks 6 a-6 e of the rotor 2 are formed with stepped shoulders 8 that form radially directed annular surfaces and axially directed annular surfaces that fit complementarily together, ensuring that these disks 6 a and 6 e are perfectly coaxial. Fasteners indicated schematically at 13 secure the disks 6 a-6 e radially together. These disks 6 a-6 e of the rotor 2 are of different diameters and have frustoconical outer surfaces that merge to form a frustoconical outer surface 9 that tapers axially and is centered in the axis 10. The diagrammatically illustrated blades/vanes 14 project radially from this surface 9 at each of the disks 6 a-6 e.

FIG. 2 shows a possible embodiment of the magnetic bearing arrangement of shaft 5. It comprises a radial magnetic bearing 4 that acts directly on the shaft 5. An axial magnetic bearing 3 interacts with a bearing disk 11 that is fixed to the shaft 5. In addition, a backup bearing 12 is provided in the event the active magnetic bearings 3 and 4 fail. 

We claim:
 1. In a turbomachine for use as a compressor and having: a tubular housing centered on an axis; a rotor at least generally centered on the axis in the housing; and bearings supporting the rotor in the housing for rotation about the axis, the improvement wherein the rotor is formed by: a small-diameter shaft extending along and centered on to the axis, formed with at least one mounting collar, and carried by the bearings; and a plurality of annular disks fitted axially together and formed with radially outwardly extending vanes, one of the disks being fitted with and secured to the mounting collar.
 2. The turbomachine defined in claim 1, wherein the shaft is formed with two of the collars offset axially from each other and each fitted with a respective one of the disks.
 3. The turbomachine defined in claim 2, wherein the disks between the disks fitted to the collars are out of engagement with the shaft.
 4. The turbomachine defined in claim 2, wherein the collars are axially between the bearings.
 5. The turbomachine defined in claim 4, wherein the bearings include two magnetic axial-thrust bearings and two magnetic radial-thrust bearings.
 6. The turbomachine defined in claim 1, the vanes are constructed to advance a fluid axially through the housing on rotation of the rotor.
 7. The turbomachine defined in claim 1, wherein the disks have end flanges forming axially and radially directed annular surfaces that fit complementarily together between adjacent disks.
 8. The turbomachine defined in claim 1, wherein the disks have between the respective vanes outer surfaces centered on the axis and of different diameters from disk to disk.
 9. The turbomachine defined in claim 8, wherein the outer surfaces are flush with one another and form a frustocone centered on the axis.
 10. The turbomachine defined in claim 1, wherein at least one of the bearings is a magnetic bearing.
 11. The turbomachine defined in claim 1, wherein at least one of the bearings is a hydrodynamic bearing.
 12. The turbomachine defined in claim 1, wherein at least one of the bearings is a roller bearing. 